<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
         var arr = [
            {name:"html",value:"12px"},
            {name:"css",value:"13px"},
            {name:"js",value:"14px"}
        ]
        var nums=[];
        arr.map(function(item){
           var value = parseInt(item.value)
           nums.push(value*2);
        })
        console.log(nums.join('-'));
    </script>
</body>
</html>